Conventional can body making machines employ a removable tool pack assembly and a removable stripper assembly which are removably mounted in a forming cavity in the machine as generally shown and described in U.S. Pat. Nos. 3,167,044; 3,289,453; 3,312,097; 3,314,274; 3,353,394; 3,359,775; 3,379,153; 3,390,565; 3,399,558; 3,457,766; and 3,469,432. Conventional stripper assemblies comprise annular ring support structure mounting a plurality of separate circumferentially spaced gripping finger members mounted in side by side abutting arrangement in a circular array. The gripping finger members are individually radially inwardly and outwardly displaceable by force of engagement with either the punch member during retraction of the punch after a forming stroke or the can body member on the punch member during the forward forming stroke. Each gripping finger member is provided with a radially innermost machined and hardened edge along which contact is made with the punch or the can. The finger members are held in position by O-ring or garter spring type resiliently deflectable devices which exert a force causing the finger members to be biased toward a radially innermost location defining a more or less circular opening having a diameter less than the outside diameter of the punch and the outside diameter of the can body. These devices also enable the finger members to be radially outwardly displaced to accommodate passage of the punch and the can body through the opening. When the can body on the punch is pushed through the opening, a portion of the inner edge of each finger member rides on the outer surface of the can body until the rim of the can body has passed beyond the inner edges. Then the finger members are moved radially inwardly by the resiliently deflectable devices to cause engagement with the outer peripheral surface of the punch. When the punch is retracted, the finger members engage the end of the can body to prevent rearward movement thereof with the punch. At the same time, compressed air applied through an axial passage in the punch blows the can body away from finger members.
The engagement of the finger members with the can body and the punch causes wear of the finger members, the outer surface of the can body and the outer surface of the punch. The finger members and the punches may be repaired by machining when the amount of wear causes manufacturing problems. The machining causes a reduction in diameter of the punch and an increase in the diameter of the opening formed by the finger members. When the difference between the diameter of the punch and the diameter of the opening reaches a certain amount, the stripping apparatus is no longer operative and the finger members and/or the punch must be replaced. The foregoing problems have led to the practice of keeping a large supply of sets of variable diameter finger members and variable diameter punches so that different diameter combinations of sets of finger members and punches may be employed to obtain a minimum diameter differential suitable for satisfactory manufacturing operations. Even so, at some point in time, the worn finger members and the worn punches must be discarded and replaced with new finger members and new punches. The repair and replacement of finger members and punches constitutes a substantial cost of manufacture.